1. Field of the Invention
The present invention relates to a light guide plate used in a liquid crystal display (LCD), and to a plane light source using the light guide plate.
2. Description of Prior Art
In a backlight type liquid crystal display (LCD), a plane light source (or “backlight system”) is used to provide bright and uniform illumination. Generally, the backlight system comprises a light source, a reflection plate, a light guide plate, a diffusing plate, and a prism layer. The light guide plate is a key component of the backlight system, and includes one or more light incidence surfaces and a light emitting surface. The diffusing plate is usually disposed on the light emitting surface, in order to make the light more uniform.
FIG. 4 shows a light guide plate 100 as disclosed in Taiwan patent No. 487170 issued on May 11, 2002. The light guide plate 100 comprises a base plate 110 and a plurality of round protrusions 120. The base plate 110 has a light incidence surface 111, a light emitting surface 113, and a bottom surface 115 opposite to the light emitting surface 113. The protrusions 120 are disposed on the light emitting surface 113.
The protrusions of the light guide plate 100 can diffuse incident light rays, so that light emitted from the light guide plate 100 is more uniform. However, this configuration does not improve the brightness of outgoing light. The brightness of outgoing light is perhaps equally important or even more important than the uniformity of outgoing light.
It is desirable to provide a light guide plate and a plane light source incorporating the light guide plate which make good the above-described deficiency.